Add missing OpenWebUI deployment guide and restructure AI hosting documentation

[Copilot]

Plan: Fix Missing OpenWebUI Setup Guide

• Create English OpenWebUI deployment guide at docs/guides/apps/openwebui.md
• Create German OpenWebUI deployment guide at i18n/de/docusaurus-plugin-content-docs/current/guides/apps/openwebui.md
• Fix broken link in English AI hosting examples page
• Fix broken link in German AI hosting examples page
• Test build to ensure documentation compiles correctly
• Address code review feedback (Round 1)
  • Change bash code blocks to shellsession format with user@local $ prefix
  • Add environment variable method for connecting to mittwald AI Hosting (recommended approach)
  • Remove duplicate sentence in introduction
  • Update DOCS.instructions.md with shellsession guideline
• Address code review feedback (Round 2)
  • Restructure content between deployment guide and AI hosting examples page
  • Move RAG section to AI hosting examples page
  • Move Speech-to-Text section to AI hosting examples page
  • Move Model Parameters section to AI hosting examples page
  • Add proper subheadings with anchor IDs to AI hosting examples page
  • Add cross-links between the two documents

Summary

Successfully created comprehensive OpenWebUI deployment guide with proper content separation between deployment and AI use cases:

Deployment Guide (docs/guides/apps/openwebui.md):

• Container deployment using mStudio UI, mw container run, and mw stack deploy
• Basic connection setup to mittwald AI Hosting (environment variables and admin panel)
• Domain assignment and operation guidance
• Cross-link to AI hosting examples for advanced AI use cases

AI Hosting Examples (docs/platform/aihosting/examples/openwebui.mdx):

• Restructured with clear subheadings and anchor IDs
• Connecting to mittwald AI Hosting (two methods)
• Optimizing model parameters
• RAG (Retrieval-Augmented Generation) setup with embedding models
• Speech-to-Text configuration with Whisper model
• Cross-link to deployment guide

Both English and German translations updated with consistent structure. Fixed broken links in AI hosting examples pages. Proper shell command formatting with shellsession code type.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Missing setup guide for Open WebUI behind the provided link</issue_title>
<issue_description>### Affected URL

(https://developer.mittwald.de/de/docs/v2/platform/aihosting/examples/openwebui/)

Describe the issue

Description

1. If you navigate to Platform → AI‑Hosting → Examples → Open WebUI.
2. the link there claims to lead to a “guide for setting up in Container Hosting.”
3. Clicking the link takes the user to the Applications area instead.
4. In that section there is no documentation for deploying Open WebUI.

Expected behavior
The link should open a dedicated guide that explains how to deploy Open WebUI in the Container Hosting environment.

Actual behavior
The link redirects to the generic Applications page, where the required Open WebUI setup instructions are absent.</issue_description>

<agent_instructions>Provide a draft for the OpenWebUI deployment guide. Refer to https://docs.openwebui.com/getting-started/quick-start for setup instructions using Docker, and to https://developer.mittwald.de/docs/v2/platform/aihosting/ and its subpages for usage instructions of the mittwald AI hosting.

Also fix the broken link mentioned in the original bug report.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Missing setup guide for Open WebUI behind the provided link #949

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[gandie]

Thanks for filling the gap, LGTM!